agent unreachable

Hi,
I have installed agent 10g on unix machine(HPUX-11.1) agent runs for 6-8 hrs
after that it dies out and when i see the instance on that server through grid control it says agent unreachable , iam not sure whats happening here.

The agent on another server which has exact same number of maxfiles(2048)runs
with no issues why is that this (server)has an issue with it,is it got to do with the number of instances running on the box or memory?